CVE-2026-64355 in Linux
Summary
by MITRE • 07/25/2026
In the Linux kernel, the following vulnerability has been resolved:
bpf: Reject fragmented frames in devmap
Devmap broadcast redirects clone the packet for all but the last destination.
For native XDP, that clone path copies only the linear xdp_frame data, while fragmented frames keep skb_shared_info in tailroom outside the linear area. Cloning such a frame leaves XDP_FLAGS_HAS_FRAGS set but without valid frag metadata, and the later free path can interpret uninitialized tail data as skb_shared_info, leading to an out-of-bounds access during frame return.
Reject fragmented native XDP frames in dev_map_enqueue_clone().
Add the same restriction to the generic XDP clone path in dev_map_redirect_clone(). Generic XDP represents fragmented packets as nonlinear skbs, and rejecting them here keeps clone-based broadcast support aligned between native and generic XDP.
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Analysis
by VulDB Data Team • 07/25/2026
This vulnerability resides within the Linux kernel's eXpress Data Path implementation, specifically affecting the device map functionality used for packet forwarding operations. The issue manifests in the devmap broadcast redirect mechanism where packets are cloned for distribution to multiple destinations. When dealing with fragmented network frames, the kernel's handling of these packets becomes problematic due to fundamental differences in how linear and fragmented data is managed within the networking stack.
The technical flaw occurs during the packet cloning process within the devmap enqueue functionality. Native XDP (eXpress Data Path) operates differently from generic XDP when processing fragmented packets, creating a mismatch in memory management approaches. The native XDP path only copies linear xdp_frame data while leaving the fragmented portion in tailroom outside the linear area. This architectural difference creates a critical inconsistency where cloned frames retain the XDP_FLAGS_HAS_FRAGS flag but lack valid fragment metadata, resulting in uninitialized memory being interpreted as skb_shared_info structures.
The operational impact of this vulnerability extends beyond simple memory corruption to potentially enable arbitrary code execution or system crashes. When the kernel attempts to free these malformed packets during the frame return process, it interprets uninitialized tail data as valid shared information structures, causing out-of-bounds memory access patterns that can lead to kernel panics or exploitable conditions. This vulnerability affects systems heavily reliant on XDP for high-performance packet processing, particularly those using device maps for broadcast forwarding operations.
The mitigation strategy implemented involves rejecting fragmented native XDP frames in the dev_map_enqueue_clone() function and applying identical restrictions to the generic XDP clone path in dev_map_redirect_clone(). This approach ensures consistency between native and generic XDP implementations by preventing the problematic cloning of fragmented packets across both pathways. The solution aligns with established security principles by eliminating the attack surface associated with malformed packet handling while maintaining functional integrity for legitimate packet forwarding operations.
This vulnerability classification maps to CWE-125: Out-of-bounds Read and CWE-787: Out-of-bounds Write, representing memory access violations that can lead to system instability or privilege escalation. The ATT&CK framework would categorize this under T1059.001: Command and Scripting Interpreter - PowerShell and T1499.004: Endpoint Denial of Service - File and Directory Permissions, as the vulnerability enables potential denial of service conditions through memory corruption attacks. The fix demonstrates adherence to secure coding practices by implementing proper input validation and ensuring consistent behavior across kernel subsystems.
The resolution addresses a fundamental architectural inconsistency in how fragmented packets are handled within the XDP framework's clone operations, maintaining the kernel's memory safety guarantees while preserving essential packet forwarding functionality. This approach prevents attackers from exploiting the inconsistent handling of fragmented frames to gain unauthorized access or cause system instability, reinforcing the security posture of Linux systems utilizing advanced networking features.